Lilienbaum A, Paulin D
Laboratoire de Biologie Moléculaire de la Differentiation de l'Université Paris 7, France.
J Biol Chem. 1993 Jan 25;268(3):2180-8.
The molecular basis for transactivation of the human vimentin gene by the Tax protein from the human T-cell leukemia virus (HTLV-1) is analyzed in this report. We first demonstrate that the factor NF-kappa B binds to the vimentin promoter. Using gel retardation assays, we found the putative NF-kappa B protein. Specific antibodies and competition experiments between the NF-kappa B-binding site in the interleukin-2R alpha and HIV-1 promoters and the vimentin promoter show that the three sites have identical affinity for the factor. We further show that the mechanisms of activation of NF-kappa B by the Tax protein involve a cellular inducer. Nuclear extract from lymphoid cells expressing Tax can induce in vitro a NF-kappa B binding activity in nonlymphoid cytosolic extract. This inducer, if preexisting in an inactivate state in T-cells which are not expressing Tax, cannot be switched to an active state by addition of partially purified Tax protein. While found in the nucleus of Tax-expressing cells in our experiments, this inducer might be cytoplasmic as well. In a first attempt to identify and characterize the inducer, we present the results of fractionation assays of nuclear extract.
本报告分析了来自人类T细胞白血病病毒（HTLV-1）的Tax蛋白对人类波形蛋白基因反式激活的分子基础。我们首先证明了核因子κB（NF-κB）与波形蛋白启动子结合。通过凝胶阻滞试验，我们发现了假定的NF-κB蛋白。特异性抗体以及白细胞介素-2Rα和HIV-1启动子中的NF-κB结合位点与波形蛋白启动子之间的竞争实验表明，这三个位点对该因子具有相同的亲和力。我们进一步表明，Tax蛋白激活NF-κB的机制涉及一种细胞诱导剂。表达Tax的淋巴细胞的核提取物可在体外诱导非淋巴细胞胞质提取物中的NF-κB结合活性。这种诱导剂，如果在未表达Tax的T细胞中以失活状态预先存在，则不能通过添加部分纯化的Tax蛋白而转变为活性状态。虽然在我们的实验中发现这种诱导剂存在于表达Tax的细胞的细胞核中，但它也可能存在于细胞质中。在首次尝试鉴定和表征该诱导剂时，我们展示了核提取物分级分离试验的结果。
